1. Field
The disclosed subject matter relates to a vertical pin integrated circuit probing device, and more particularly to a multi-offset die head for loading probes having different offsets into a die head assembly of the vertical pin integrated circuit probing device.
2. Description of the Related Art
One of the challenges of vertical buckling beam (VBB) probe technology is the ability to probe very tight pitch peripheral pads. This has conventionally been done with cantilever-style probe cards. A cantilever card consists of rows of wires suspended substantially horizontally over the device to be tested. The tips of the wires are bent down, and are tapered down to a point which contacts the pads on the chip. The tight pitch requires having multiple layers of overlapping probes. Since the tips are free-floating, their location must be fine-adjusted by manually bending the wire such that the probe tip aligns with the center of the pad being tested. Periodic re-adjustment of the tips is necessary, creating a maintenance issue for the user. The overlapping nature of the design also requires long probe needles which results in increased probe inductance and limits the number of chips that can be probed simultaneously.
One difficulty with using VBB probes for tight pitch peripheral bond pad applications is the difficulty in making a reliable contact between the head of the probe and the space transformer pad. This is not an issue with cantilever cards because the base of the cantilever contact is soldered directly to the PCB. In contrast, the heads of VBB probes float inside micro-holes that are drilled into the probe head upper die. These upper die micro-holes are normally over-sized relative to the holes in the lower die to facilitate assembly of the upper die over the heads of all the contacts simultaneously. The contact heads and the space transformer pads may not be perfectly aligned due to the oversized upper die holes, potential misalignment between the upper die with the space transormer, differences in thermal expansion of the head and space transformer, head scrub, etc. It is therefore desirable to have as large a pad as possible to accomodate any misalignment.
Larger pads can sometimes be accommodated in tight-pitch in-line pad arrangements by “spinning” the contacts. By rotating the contacts slightly, it is possible to move the heads of neighboring probes further apart, allowing for the use of larger space transformer pads. However, for in-line arrangements where there are long continuous rows of pads without gaps, this is often not possible. In a peripheral pad arrangement, the pads on the chip are generally very narrow and rectangular in shape and it is desirable to align the contact such that the contact “scrubs” along the long direction of the pad. Since this precludes “spinning” the contacts, the heads of the VBB probes end up aligned at the same pitch as the pads on the chip being tested. The tight pitch of these peripheral bond pads prevents the use of oversized pads. In addition, because the pitch is so tight, over sizing the upper die holes would not be possible with a conventional VBB probe design, thereby making the assembly process very difficult. U.S. Pat. Nos. 6,297,657 and 6,633,175 disclose vertical pin probing devices and are incorporated by reference as if fully disclosed in their entireties herein.